1. Technical Field
The present invention relates to a liquid crystal display panel and more particularly, to a liquid crystal display panel and a method of fabricating the same capable of preventing a gravity defect of the liquid crystal display panel to improve a picture quality.
2. Description of the Related Art
In general, a liquid crystal display (LCD) device controls the light transmittance of liquid crystal cells using electric field to thereby display a picture.
To this end, the LCD device includes a liquid crystal display panel having liquid crystal cells arranged in an active matrix, and driving circuits for driving the liquid crystal panel.
The liquid crystal display panel is provided with pixel electrodes and a reference electrode, i.e., a common electrode, to supply the electric field to each of the liquid crystal cells.
Usually, each of the pixel electrodes is formed for each liquid crystal cell on a lower glass, while the common electrode is formed as an integrated whole on the entire surface of an upper glass. Each pixel electrode is connected to a thin film transistor (TFT) that is used as a switching element.
The pixel electrode together with the common electrode drives the liquid crystal cell in response to data signals supplied via the TFT.
FIG. 1 is a perspective view illustrating a related art liquid crystal display panel.
Referring to FIG. 1, there is shown a liquid crystal display panel in accordance with the related art, which includes upper and lower array substrates 10 and 20 combined together, and a liquid crystal material 8 between the upper and the lower array substrates 10 and 20.
The liquid crystal material 8 rotates, in response to an electric field supplied thereto, to thereby adjust the transmittance of incident light via the lower array substrate 20.
The upper array substrate 10 includes a color filter 4, a common electrode 6 and an upper alignment film (not shown), formed on a rear surface of the upper glass 1.
The color filter 4 includes color filters of red (R), green (G), and blue (B) and makes it possible to display colors by passing light having a specific wavelength band. A black matrix 2 is placed between the color filters 4 adjacent each other and prevents the degradation of the contrast ratio by absorbing the light incident from the adjacent cells.
The lower array substrate 20 includes: a data line 18 and a gate line 12, which cross each other and are insulated each other by a gate insulating layer located therebetween, formed on the entire surface of the lower glass 21; and further a TFT 16 at the crossing of the data line 18 and the gate line 12.
The TFT 16 includes: a gate electrode connected to the gate line 12; a source electrode connected to the data line 18; and a drain electrode facing the source electrode with a channel portion including an active layer and an ohmic contact layer therebetween. The TFT 16 is connected to the pixel electrode 14 via a contact hole passing through a passivation film.
In response to gate signals from the gate line 12, the TFT 16 selectively supplies data signals from the data line 18 to the pixel electrode 14.
The pixel electrode 14 is made from a transparent conductive material having a high light transmittance and is in a cell region formed by the data line 18 and gate line 12.
The pixel electrode 14 generates a potential difference along with a common electrode 6 by data signals supplied via the drain electrode. Under the influence of the potential difference, the liquid crystal material 8 between the upper and lower substrates 1 and 21 rotates due to the dielectric anisotropy thereof. Hence, the light supplied via the pixel electrode 14 from the light source passes toward the upper substrate 1.
Spacers maintain the cell gap between the upper and the lower array substrates 10 and 20. A sealant 55 is applied in a rectangular form as shown in FIG. 2 to the upper array substrate 10 or the lower array substrate 20. Thereafter, the upper array substrate 10 is combined with the lower array substrate 20. And then, the liquid crystal material 8 is injected through a liquid crystal injection hole 55a in an inner space provided by the spacer 22.
According to the related art liquid crystal display panel formed by above-mentioned method, if the liquid crystal material 8 injected between the upper array substrate 10 and the lower array substrate 20 is exposed to a high temperature, a defect due to gravity (hereinafter, referred to as a gravity defect) occurs. The gravity defect occurs because the liquid crystal material flows in the direction of gravity to thereby deteriorate the picture quality.
More specifically, after the liquid crystal material 8 is injected into the inner space provided by the spacer 22, a voltage is supplied to the common electrode 6 formed on the upper glass 1 and to the pixel electrode 15 formed on the lower glass 21 in order to operate the liquid crystal display panel. The supplied voltage raises the temperature of the inner space provided by the spacer 22. As a result, a volume of the liquid crystal material 8 in the inner space expands. As shown in FIG. 3A, the cell gap thus becomes large due to the expanded liquid crystal material, so that the spacer 22 is separated from the upper glass 1 or the lower glass 21 and the expanded liquid crystal material 8 flows in the gravity direction, to thereby cause the gravity defect and distort at least one of the upper glass 1 and the lower glass 21. Accordingly, as shown in FIG. 3B, a stain 65 appears in a region where the liquid crystal material is over-filled, which results in deterioration of the picture quality.